| Calculations of the deformation of the director in the liquid crystal cell and change with electric field are thought as the basis for studying display characteristics of liquid crystal devices. Solving differential equation definite conditions problem is the standard method to calculation the deformation of the director in the liquid crystal cell. But to a lot of questions, there are seldom analytic solutions and are usually calculated by numerical method. The relaxation method is a numerical calculation method to solve two boundaries problem. In this paper we use relaxation method to solve the boundary problem. To calculate the distribution of the director of super twisted nematic liquid crystal cell with strong and weak anchoring respectively under electric field. The results show that the change of the tilt angle of director increases with the increase of electric field or decrease of the anchoring. And the threshold voltage of LCD decreases with the increase of the anchoring.Super twisted nematic (STN) has steep electro-optical characteristic curve, so it can be used in multiplex drive. But because of birefringence effect, there has serious color shift. There have some colors, such as yellow or blue, as the cell is in off-state (non-voltage added). This colored background of STN is illcome for people who accustom to black-white display. And from the conditions at present, black-white display is necessary condition to get colored display by insetting filter film. So it is very necessary to realize black-white STN display.Some people propose double cells to compensate which can banish the color in display, but it add the volume, weight and production cost of LCD. Uniaxial birefringence film can banish the disadvantage of double cells and can gain black-white compensation's end. Film compensation LCD can be classified into single film and double films compensation.The optical characteristics for STN-LCD with film compensation are determined mainly by the anisotropy of refractive index of liquid crystal material, the distribution of director in liquid crystal layer, the orientation of polaroids and the compensating films' orientations and their optical retardations. In this thesis, by simulating the director alignment, using the characteristics of optical transmission, taking Jones matrix we calculate the transmittance of the LCD. By theoretically studying to compensating-film from different aspects, single film and double films, we get that the double-film-compensation has nice compensating effect, especially put the two films in the two sides of LC layer.11In this thesis we optimize six parameters, the orientation for optical axes of polaroids and compensating films and the optical retardation of two compensating films, and get the conclusion that at off-state the transmittance is less than 0.003 for the wavelength in the visible light, which can realize black-white display well.
|
PDF Full Text Request